3D Models
Thingiverse or MakerBot's Thingiverse - a thriving design community for discovering, making, and sharing 3D printable things.
Yeggi - Search engine for 3D printable models.
3D Warehouse - 3D Warehouse contains millions of models created in SketchUp.
Repair 3D Models
Microsoft 3D Model Repair service
Use the Microsoft 3D Model Repair service to repair STL, OBJ, 3MF or VRML files automatically. This service will save you time by taking care of the many common errors in 3D models that otherwise would require manual repair by a dedicated designer. The service closes holes in the model, fixes face normals, removes self-intersections, and more. You'll be more productive and be on your way to more reliable 3D manufacturing in minutes!
3D Printing Marketplace
Shapeways and Sharpen 3D are 3D Printing marketplace and community. They provide platforms for anyone who wants to create, buy, and sell products with 3D Printing.
Mobile Apps